Flow rates of multi-phase streams, such as those including suspended solids, have been measured by cross correlation of upstream and downstream detector outputs based on the time change required for suspended solids to flow from the upstream detector to the downstream detector. Procedures of this type may not be of adequate dependability if, for example, disturbances occur in the multi-phase stream to scramble the position or orientation of the suspended solids being tracked during transit thereof between the two detectors. Such scrambling may occur particularly in turbulent stream flow.
Where two or more spaced probes are utilized, alignment of the probes is essential with respect to the direction of stream flow. Additionally, use of multiple spaced probes inherently extends the time in which a desired analysis of a multi-phase stream flow can be accomplished.
In some systems autocorrelation of the product of spaced detector outputs is utilized. Generation of beat frequencies between the detectors is established resulting from flow-induced Doppler shifts arising from the occurrence of disturbances upstream and downstream. However, in utilizing the frequency of these beats, the autocorrelation of the product of the signals from the detectors becomes rather complex.
In an effort to stabilize flow to permit more accurate determinations of flow rates, a system utilizing a vortex-producing member located upstream from a pair of spaced probes has also been proposed. A series of time-related vortices is generated and autocorrelation of the outputs of the spaced probes, based on the time period between consecutively generated vortices, are averaged.
Still another approach to the determination of flow rate of a multi-phase stream involves fiber optic illumination of at least a segment of the stream and the transmission of images of particles flowing past an endoscope as recorded with a camera and viewing monitor. Presumably, image analysis can be relied upon to obtain flow rate.
Other systems in use include the use of optical fibers to measure bubble flow rate and size. One such system relies on Doppler shifting of monochromatic light. In the operation of this system a bubble impinges on the end of an optical fiber with the fiber penetrating the first surface portion of the bubble and subsequently the second surface portion in order to obtain a flow-by measurement.
As has been explained, the majority of known systems rely on cross correlation techniques. Alignment of the sensors is critical in effective use of such techniques. Additionally, two channels of data need to be sensed and processed. The present invention constitutes a substantial improvement over known flow rate determination procedures.